SQL/MX Programming Manual for C and COBOL (G06.24+, H06.03+)

Dynamic SQL With Descriptor Areas

HP NonStop SQL/MX Programming Manual for C and COBOL—523627-004

10-15

Prepare the SQL Statement

Example

desc_max = 1;

EXEC SQL ALLOCATE DESCRIPTOR 'in_sqlda' WITH MAX :desc_max;

This descriptor area can hold only one dynamic input parameter in the prepared

statement.

Allocating the Output SQL Descriptor Area

The number of item descriptor areas for the output SQL descriptor area must be large

enough to hold all the columns of the table referred to in the prepared statement.

Example

desc_max = 6;

EXEC SQL ALLOCATE DESCRIPTOR 'out_sqlda' WITH MAX :desc_max;

This descriptor area can hold up to six columns selected from the table referred to in

the prepared statement.

Prepare the SQL Statement

To execute the dynamic SQL statement, first prepare the statement you have

constructed from user input and stored in a host variable. The PREPARE statement

checks the statement syntax, determines the data types of any parameters, and

compiles the statement. The PREPARE statement also associates the prepared

statement with a name you can use in subsequent EXECUTE statements.

Use this general syntax:

For complete syntax, see the PREPARE statement in the SQL/MX Reference Manual.

Example

EXEC SQL PREPARE sqlstmt FROM :hv_sql_statement;

The SQL identifier sqlstmt is the name of the prepared statement to be used in a

subsequent EXECUTE statement. The host variable hv_sql_statement contains

the dynamic SQL statement you have constructed from user input.

Describe the Input Parameters and the Output Variables

To provide information necessary for the execution of the dynamic SQL statement, you

must describe the dynamic input parameters and the output variables in the prepared

statement. See Describing Input Parameters on page 10-4 and Describing Output

Variables on page 10-7.

PREPARE SQL-statement-name FROM :SQL-statement-variable